The proliferation of smartphones and other mobile devices has placed heavy data traffic demands on cellular networks, with cellular network operators facing difficult challenges in meeting this demand given their existing spectrum allocations. Recent policy shifts at the federal levels and Department of Defense indicate that sharing existing federal spectrum with commercial users may be a viable option for meaningful increase of spectrum for Long Term Evolution (LTE) fourth generation (4G) cellular technologies. Making more spectrum available will certainly provide opportunities for mobile broadband capacity gains, but only if those resources can be efficiently accessed such that secondary users can proactively share the same bands as the primary users (e.g., federal incumbent users). Effectively grafting pre-emptible spectrum into a cellular network is challenging. Past approaches to coexistence with primary users centered on spectrum sensing-based dynamic spectrum access (DSA) techniques and database driven DSA techniques.
Spectrum sensing DSA approaches entail the use of sensing devices to scan a frequency band of interest to identify unused spectrum where secondary access is possible without impacting primary user operations. The main approaches can be categorized as internal (co-located) sensing, external sensing, use of beacons, and database driven techniques, and have included algorithms for matched filtering, energy detection, cyclostationarity, radio identification based sensing, waveform based sensing, etc. So-called cooperative spectrum sensing increases sensing accuracy by fusing data from multiple nodes and thus takes advantage of spatial diversity. General types of cooperative spectrum sensing include centralized, distributed, external, or device centric (local) sensing.
Database driven DSA is a sub-class of the sensing based DSA approach. The database driven approach is classified into two general categories: geo-location based and interference based. Both are similar in principle that they provide a database to the secondary users (cellular network operators) which helps them transmit in licensed bands while ensuring they do not interfere with primary users in the given band. These databases can be stored at eNodeBs or at the network level and have different levels of granularity. In the past, these databases only provided coarse resolution of historical spectrum use by primary users. A type of database called a radio environment map (REM), which can contain interference information, have been utilized to help in deploying secondary networks. However, each of these approaches has shortcomings, especially when mobile users, hidden nodes, and interaction with the incumbent or primary users are considered.
Therefore a need exists for an improved system and method for temporal and geographical spectrum sharing between a commercial cellular operator and a government incumbent operator.